1. Field of the Invention
The present invention relates to a method for operating a control unit that is able to assume multiple states. Furthermore, the present invention relates to a corresponding control unit, as well as a computer program and a computer program product for implementing the described method.
2. Description of Related Art
In the event of a change to a system state, it is known to carry out an initialization of the new state to be activated in a finite time that is as short as possible rather than carry out an abrupt change of state. During this initialization, in addition to initialization components, functionality from the old state is processed in a fast time slot pattern and functionality from the new state is processed in a slow time slot pattern. In this implementation, allowance must be made to ensure that RAM cells in slow time slot patterns are provided for further processing in fast time slot patterns. In this context, the problem arises that initializations that have been carried out are undone again during the transition when jointly-used RAM cells are accessed from the old state before it is ultimately possible to completely switch to the new state.
Furthermore, an abrupt switch is known in which all functions must provide that the input variables necessary for a calculation are available on time. This is achieved by processing the input variables in the time slot patterns in which they are also consumed. This procedure causes a higher runtime load relative to an implementation of the method described above.
A method and a device for starting up a control unit for a motor vehicle are known from published German patent document DE 199 63 214. In it, the following steps are provided: Checking whether a process to be monitored was started before the reset of the control unit; continuation of the process to be monitored if the process to be monitored was started before the reset of the control unit; and starting of the process to be monitored if the process to be monitored was not started before the reset of the control unit.
Published German patent document DE 103 60 200 describes a method and a device for operating a control unit. The control unit contains control unit software and this control unit software or parts of it may assume multiple states, each state being represented by at least one value of at least one state variable. In this context, a transition from a first state into a second state corresponds to a change of the value of the state variable, and a distinction is made between a first internal value of the state variable and a second external value of the state variable, both values being the same after the transition to another state has been carried out, and the change of the external value proceeding in a delayed manner relative to the change of the internal value. Thus, an optimization with regard to runtime and resource consumption is achieved.